Adhesive compositions based on 2-cyanoacrylates may be used as single-part liquid adhesives for bonding a variety of materials. Examples of materials to which adhesive bonds can be formed by use of 2-cyanoacrylate adhesives include metals, plastics, glass and rubbers, and such materials are met with as parts of precision instruments and household articles. It has also been proposed to use cyanoacrylate based adhesives for bonding blood vessels, living tissue in surgical operations, and vegetable tissue in grafting.
Although adhesive compositions based on 2-cyanoacrylates are potentially suitable for use in a wide variety of applications, they tend to have various attendant problems including ones relating to storage stability, cure speed and bond performance.
When 2-cyanoacrylates are stored even in tightly closed vessels they exhibit a tendency to polymerize within a relatively short period of time at normal room temperatures. At higher temperatures this tendency to polymerize is enhanced. It has been proposed therefore to include in adhesive compositions based on 2-cyanoacrylates anionic polymerisation inhibitors, e.g., P.sub.2 O.sub.5 or SO.sub.2, in combination with a free radical polymerization inhibitor, e.g., hydroquinone or monomethyl ether of hydroquinone.
Compositions based on 2-cyanoacrylates containing anionic polymerization inhibitors and free radical polymerization inhibitors have not generally fully overcome difficulties associated with cure speed and bond performance. Cure speed difficulties in general appear to result from a lack of tackiness of the composition necessitating holding of parts to be bonded in appropriate correlation with the adhesive betweem them until the 2-cyanoacrylate polymerises, and builds up sufficient bonding strength. Bonds formed with 2-cyanoacrylates tend to be rather brittle, become unreliable when aged and tend not to resist strongly deterioration caused by heat.